Solid fired hot gas generator with extended regulating range

ABSTRACT

The invention relates to a solid fired hot gas generator which comprises a plurality of solid burners for extending the regulating range, which form a multiple solid burner with an enlarged regulating range. A solid feed and a combustion air feed are assigned to each solid burner and with the aid of a dosing means a separate, dosed solid feed to each solid burner is guaranteed. The firing power of the multiple solid burner which is in particular a multiple impulse burner extends from the minimum power of one of the solid burners to the maximum power of all solid burners so that a regulation of all necessary load regions of a plant unit to be supplied is covered.

The invention relates to a solid fired hot gas generator with anextended regulating range which can preferably be used ingrinding-drying installations, for example for grinding solid fuels.

Coal grinding plants with an air swept mill, for example a verticalroller mill of the LOESCHE type, a suspended roller mill or a ringroller mill, in which wet raw coal is subjected to a grinding-dryingprocess with the supply of hot gas and ground to coal dust, with aseparating unit, for example a filter, in which the coal dust-gasmixture is separated, and with a hot gas generator for generating thehot gas, to which a part of the gas is fed back as return gas, are knownfrom coal gasification, pig iron and steel production with PCI(Pulverised Coal Injection) processes and from the cement industry (DE40 35 730 C2, catalogue of LOESCHE GmbH, Düsseldorf, “Loesche-Mühlen fürfeste Brennstoffe”, 01/2008).

Coal dust fired hot gas generators are additionally used in thenon-metallic minerals industry to dry raw meal, slag and granulatedblast furnace slag and cement. Hot gas generators which are fired withbrown coal or hard coal dust are also known in the gypsum, sugar andpotash industry.

A hot gas generator with a burner which is fired with pneumaticallyconveyed combustion dust, for example hard coal or brown coal dust,biomass dust or mixtures thereof, with the supply of combustion air, aburner muffle arranged on the outlet side on the burner, a feed for thegas to be heated and a mixing component which is arranged after theburner muffle and formed as a perforated jacket (LOMA) with staggeredcylinder portions and with a protective jacket forms an annular channelfor the gas to be heated is known from DE 197 06 077 A1.

The hot gas generator described in DE 42 08 951 A1 already comprises aperforated jacket unit made of metal for flowing in of the gas to beheated and a burner muffle which is formed to be substantially shorterin axial direction than the perforated jacket unit and is lined with afire-resistant material. The burner is here, however, a multi-lanceburner with lean gas-combustion air nozzles surrounding each other.

DE 197 25 613 A1 discloses a burner for generating hot waste gases bycombusting heating oil or heating gas or coal dust. The coal dust istransported with a gaseous carrier medium, preferably air, and isinjected through an injection lance, which extends from the burner headto the point of the largest diameter of a conical reaction chamber andis provided at the outlet side end with a deflection hood, into thereaction chamber. The combustion air is fed via a radial blade cascadeat the head-side end of the reaction chamber. The blade cascade and apart of the reaction chamber are surrounded by an air collectinghousing, in which the combustion air is to be settled and from which thecombustion air passes via the blade cascade into the reaction chamber.The burner generates, as a consequence of its flow pattern, aparticularly large area of turbulent fluctuation movements. Thecombustion dust is transported back to the air guide blades afterleaving the deflection hood and is heated by a swirling, screw-likeflame to approximately 1000° C. and ignited. The flame jet has a strongimpulse and produces a very rapid recirculation of the gases.

In the internet publication “Impuls-Brenner, System Dr. Schoppe, fürBraunkohlenstaub, Heizöl und Gas von 100 kW bis 35 MW” theaforementioned burner is described as an impulse burner.

A further development of the impulse burner which is to comprise anincreased flame stability and flame jet speed for a hot gas temperaturerange of at least 200° C. to 900° C. is described in DE 102 32 373 B4.

Burners for solid fuels which are used in association with mixingchambers have a regulating range of maximum 1:5. This technicallysubstantiated limitation of the regulating range makes more difficult orprevents the use of hot gas generators with mixing chambers, for examplea perforated jacket unit, in process-based installations which requirehigher regulating ranges, for example regulating ranges up to 1:10. Suchregulating ranges can be caused by greatly fluctuating moistures of thematerial to be dried and changes in the throughput of the aggregate tobe delivered.

The throughput of a vertical roller mill of the LOESCHE type lies forexample between 100% and 40%. The mill thus has a regulating ratio of1:2.5. If a minimum throughput coincides with a very low moisture and arelatively high outside temperature only a relatively low heat isnecessary. A maximum heat consumption results with a maximum throughput,a maximum moisture of the material to be ground and dried and arelatively low outside temperature.

The following concrete example is to illustrate that a regulating ratioof approximately 1:8 is necessary in order to be able to approach all“operating points”.

EXAMPLE Hard Coal

Max. case Throughput=80 t/h

Moisture=15%

Temperature=5° C.

Heat quantity=49.66×10⁶ kJ/h (13.8 MW)

Min. case Throughput=32 t/h

Moisture=5%

Temperature=35° C.

Heat quantity=6.1×10⁶ kJ/h (1.695 MW)

The regulating ratio thus amounts to: 49.66:6.1=1:8.14.

The aforementioned regulating ratio of 1:8.14 has been achieved thus farwithout a hot gas generator with a solid burner. In grinding-dryinginstallations for grinding coal, therefore, insofar as waste heat is notavailable from the process itself, predominantly hot gas generators witha gas or oil burner are used. In case of coal gasification installationsas a rule synthesis gas is fed to the hot gas generator as fuel and inPCI plants blast furnace gas for combustion. The coal grindinginstallations for coal gasification, PCI plants and in the cementindustry require regulating ranges of at least 1:8. Generally aregulating ratio of at least 1:10 for oil and gas fired hot gasgenerators is already state of the art.

It is an object of the invention to create a solid fired hot gasgenerator, in particular a coal dust fired hot gas generator, with anextended regulating range in order to be able to replace heating oil andgas by a cost-effective fuel, for example brown coal dust, hard coaldust etc. and also to be able to set aside the economically inefficientuse of synthesis gas, blast furnace gas etc. for producing hot gases inhot gas generators.

According to the invention the object is achieved through the featuresof claim 1 and claim 2. Useful and advantageous embodiments arecontained in the sub-claims and the description of the figures.

A core thought can be seen in equipping a hot gas generator with aplurality of burners in order to increase the regulating range.

According to the invention a solid fired hot gas generator comprises aplurality of solid burners in order to increase or extend the regulatingrange so that a multiple solid burner is formed.

An independent solid feed and a combustion air feed are assigned to eachsolid burner and each solid burner can be fired independently of theother solid fuels burners. The firing power of the multiple solid burnerthen extends from the minimum power of one of the solid burners to themaximum power of all solid burners provided. The regulating range isthus extended and all load regions of an aggregate, to which the hot gasproduced in the hot gas generator is supplied, can be covered.

In a preferred embodiment a hot gas generator with a burner muffle and astart burner, which is arranged in a burner plate of the burner muffle,with a feed means for the gas to be heated and with a mixing component,in which the combustion gas produced is mixed with the gas to be heated,and which is arranged after the burner muffle, comprises a plurality ofsolid burners which are arranged coaxially with the start burner andfixed in the burner plate of the burner muffle.

The number of burners can advantageously be adapted to the respectiverequirements. For example two, three or four, possibly also more solidburners can be flanged to the burner plate of the burner muffle. Burnersof equal or different size can also be advantageously used, that is tosay burners with equally large or different sized firing power.

The inventive hot gas generator is usefully designed in verticalconstruction and the multiple solid burner is designed and arranged inthe burner plate of the burner muffle so that the solid burner with itscoal dust supply and its reaction chamber extend into the burner muffle.

It is advantageous if three solid burners are arranged with equaldistance from each other and arranged coaxially with the start burnerguided on a longitudinal shaft of the burner muffle and through theburner plate. The burners can also be arranged at a defined angle insuch a way that the flue gases leaving the burners are guided to thecentre of the outlet of the burner muffle. As the solid burners areprovided for ash-containing fuels a vertically or downwardly inclinedarrangement is recommended in the burner plate or in the burner muffleof the hot gas generator.

It is further advantageous that a burner muffle which must be adaptedmerely in its dimensioning to the provided number of solid burners inthe burner plate can be used. The burner muffle can be lined with afire-resistant material.

It is also useful if the burner muffle is surrounded with a feed meansfor the gas to be heated and the gas to be heated can be fed to thesubsequent mixing component for mixing with the combustion gas produced.

A perforated jacket unit can advantageously be arranged as a mixingcomponent which is formed as a steel combustion chamber and comprises inaxial direction a plurality of cylindrical and coaxial perforatedjackets which form at their transitions annular gaps for flowing in ofgas to be heated and are surrounded by an outer, closed sheet steeljacket with the formation of an annular channel. Such a sheet steelchamber is known as a perforated jacket combustion chamber(LOMA-combustion chamber).

Impulse burners of Carbotechnik Energiesysteme GmbH, Geretsried can beadvantageously used for example as solid burners. These have beendescribed above in connection with DE 197 25 613 A1 and DE 102 32 373 B4and an internet publication of this company. However, other solidburners can also be used.

The impulse burners have powers between 0.5 and 100 MW and are suited toarrangement in an upper, end face burner plate of the burner muffle ofthe inventive hot gas generator so that a multiple impulse burner isformed.

For separate control and regulation of each individual solid burner adosing means is provided which can supply each solid burner with coaldust individually and independently of the operation of the adjacentburner and can move to each desired regulating point.

The CT dosing machine for fluidising, dosing and pneumatic conveying ofCarbotechnik Energiesysteme GmbH, Geretsried is particularly suitable.

The dosing machine is described in an internet publication of theaforementioned company and in EP 0 054 018 B1 and EP 0 210 162 B2.

The extended or increased regulating range of the inventive hot gasgenerator with a multiple solid burner or a multiple impulse burner isto be explained further below with the aid of the example described atthe start.

In this example a maximum heat quantity of 13.8 MW was necessary. Forprocess-based reasons and having regard to the incorporation of theburners in the burner muffle a number of three solid burners is selectedas an optimum arrangement. Each solid burner then has to provide a powerof 4.6 MW. In case of a regulating range of an individual solid burnerof 1:4 there is a minimum power of 1.15 MW. One thus even falls short ofthe necessary heat quantity of 1.695 MW and the regulating range of anindividual solid burner of 1:4 is extended to a regulating range of theinventive multiple burner with three solid burners to 1:12.

According to the heat requirement only one solid burner of the multipleburner arrangement or two or all three fuel burners can be brought intooperation. The overall regulating ratio then lies for the hot gasgenerator with three solid burners at 1:12.

Such a value is achieved also only in exceptional cases with gasburners.

The inventive multiple solid burner arrangement on or in the burnermuffle of a hot gas generator thus facilitates in an extraordinarilyefficient manner the production of hot gases, grinding-dryinginstallations and other thermal installations. The use of solid fuels,for example brown coal dust, which is considerably more cost-effectivein comparison with heating oil and combustion gases and is additionallyavailable in adequate quantity, is particularly advantageous. When usingblast furnace gas or synthesis gas to produce hot gases for dryingpurposes, in particular in coal grinding installations, a substitutionwith coal dust can be carried out.

The invention is explained in further detail below by reference to adescription of the figures. These show in a greatly schematisedrepresentation:

FIG. 1 an axial longitudinal section through an inventive hot gasgenerator with a multiple solid burner and

FIG. 2 a top view according to line II-II in FIG. 1.

FIGS. 1 and 2 show a hot gas generator with a multiple solid burner 10,which consists in this example of three solid burners 3, 4, 5.

It follows from FIG. 1 with two illustrated solid burners 3, 4 that asolid feed 6 and a combustion air feed 7 are assigned to each solidburner 3, 4, 5 and that the solid burners 3, 4, 5 are arranged in aburner plate 12 of a burner muffle 2. The burner muffle 2 and asubsequently arranged mixing component 9 are vertically orientated likethe solid burners 3, 4, 5 and a start burner 8.

Impulse burners for coal dust, for example brown coal dust, are used assolid burners 3, 4, 5, which comprise a conically extending reactionchamber 16 with a conically tapering flame accelerating nozzle 17, aninjection lance 18 with deflection hood 19 for injecting fluidised coaldust and a radial blade cascade 25 on the burner head, through whichcombustion air passes into the reaction chamber 16, whereby this entersvia a lateral inlet opening 7 into an air housing 28 and passes fromhere to the radial blade cascade 25 and the reaction chamber 16.

The impulse burners fired with solid fuels have a high flame jet speedand a flame 30 extends, as shown in FIG. 1, through the burner muffle 2into the mixing component 9.

If no solid fuel is available the impulse burners can be switched to gasin order to be able to maintain the operation of subsequentinstallations. Gas feeds 27 follow, besides the solid feeds 6, from FIG.1 to the solid or impulse burners 3, 4 visible here.

In the mixing component 9 the heating and mixing of the combustion gasesproduced in the multiple solid burner 10 with process gas 13 to beheated, which is fed via a feed means 11, take place.

The feed means 11 surrounds, with its radial housing, the burner muffle2, into which the solid burners 3, 4, 5 extend with their reactionchamber 16 and the flame accelerating nozzle 17.

The burner muffle 2 is lined in this embodiment with a fire-resistantmaterial 15. The fire-resistant lining can also be omitted. A perforatedjacket unit 20 is connected to the burner muffle 2 on the outlet sideand thus opposite the multiple solid burner arrangement 10 in the burnerplate 12 as a mixing component 9. This perforated jacket unit 20 is partof the steel combustion chamber and consists of a plurality ofcylindrical and coaxial perforated jackets 21 with enlarging diameters.Annular gaps 22 for flowing in of the gas 13 to be heated are formedbetween the individual perforated jackets 21 and an annular channel 24is formed between the perforated jackets 21 and an outer closed sheetsteel material 23, into which annular channel 24 the gas 13 to be heatedis fed from the feed means 11 and then via the annular gaps 22 and holesof the perforated jacket 21 into the mixing chamber 26. The hot gas 14formed is removed via an outlet opening 29.

FIG. 2 shows a top view of the hot gas generator at the height of theburner plate 12 of the burner muffle 2 with the spiral housing of thefeed means 11 for the gas to be heated arranged on the periphery of theburner muffle 2. A start burner 8, which is operated with gas or oil, isarranged in the centre of the burner plate 12 and the three solidburners 3, 4, 5 extend coaxially and at the same distance from eachother and from the start burner 8 vertically downwards.

The solid burners 3, 4, 5 used as impulse burners are also suited forthe combustion of gases. If no coal dust is available in case ofinterruption, the impulse burners can be switched without problems tonatural gas, synthesis gas or blast furnace gas so that the operation ofthe subsequent installations, for example of a power station in coalgasification, a blast furnace in PCI plants, etc., can be maintained.

An essential advantage of the inventive multiple fuel burner is theextension of the field of use of hot gas generators with solid burners.

The use of a hot gas generator with multiple fuel burners, in particularmultiple impulse burners, is a possibility in coal gasification plantsand in PCI plants in the steel industry and for non-ferrousmetallurgical processes and also in general heat-based installations.The synthesis gas produced in the coal gasification can thereby beadvantageously used in the energy producing industry and increasingly inthe plastics industry. If on the other hand synthesis gas is branchedoff as an energy carrier for the grinding-drying process this requires,with the usual heat outputs of between 10 and 30 MW, synthesis gasquantities of 3300 m_(N) ³/h to 10,000 m_(N) ³/h with a calorific valueof the synthesis gas of approximately 11,000 kJ/m_(N) ³. This representsa considerable loss for the intended use. Blast furnace gas from thesteel industry has in the meantime also been used increasinglyfrequently in special power stations for power generation. The use ofcoal dust for hot gas generation avoids the use of the abovementionedgases and other fuels such as light and heavy oil, natural gas, etc. inhot gas generators and is extraordinarily advantageous having regard toenergy and investment.

1. Solid fired hot gas generator with an extended regulating range,characterised in that a plurality of solid burners are arranged in aburner muffle and a multiple solid burner is formed, an independentsolid feed and combustion air feed are assigned to each solid burner andthe firing power of the multiple solid burner can be regulated from theminimum power of a solid burner to the maximum power of all solidburners so that load regions of a subsequent installation unit, to whichthe hot gas produced in the hot gas generator is fed, are covered. 2.Hot gas generator according to claim 1, with a start burner which isarranged in a burner plate of the burner muffle, with a feed means forgas to be heated and with a mixing component arranged after the burnermuffle, in which the combustion gas produced is mixed with the gas to beheated, characterised in that a plurality of solid burners are arrangedcoaxially to the start burner and are fixed in the burner plate of theburner muffle.
 3. Hot gas generator according to claim 1, characterisedin that solid burners of the same size or different sizes form amultiple solid burner.
 4. Hot gas generator according to claim 2,characterised in that three solid burners are arranged with an equalangular distance from each other and with an equal radial distance fromthe start burner in the burner plate.
 5. Hot gas generator according toclaim 1, characterised in that the solid burners are arranged at adefined angle to the longitudinal axis of the burner muffle.
 6. Hot gasgenerator according to claim 1, characterised in that a dosing means isprovided for a separate, dosed solid feed to each solid burner.
 7. Hotgas generator according claim 1, characterised in that dust-form fuel,in particular coal dust or biomass dust, can be fed in fluidised form tothe solid burners.
 8. Hot gas generator according to claim 1,characterised in that impulse burners, in particular for hard coal dust,brown coal dust, petroleum coke dust, biomass dust and dust mixtures,are arranged as solid burners, which respectively comprise a conicallyextending reaction chamber, possibly with a conically tapering flameaccelerating nozzle, and an injection lance with deflection hood for thefluidised, dust-form fuel and a radial blade cascade for supplyingcombustion air.
 9. Hot gas generator according to claim 8, characterisedin that the impulse burners used as solid burners can be switched to gasand operated for example with natural gas, synthesis gas or blastfurnace gas.
 10. Hot gas generator according to claim 1, characterisedin that a perforated jacket unit (LOMA) with a plurality of cylindricaland coaxial perforated jackets, with annular gaps between the perforatedjackets and with an annular channel between the perforated jackets andan outer, closed sheet steel jacket is disposed as a mixing component.11. Hot gas generator according to claim 1, characterised by use in coalgasification plants, PCI plants in the steel industry and in non-ferrousmetallurgical processes, in the cement industry and in generalheat-based installations.